The invention relates to a color measurement system for offset printing, with a color-measuring device movably disposed on a bridge which spans an original to be measured.
Various color-measuring processes are known for the measurement of color-measuring fields of a print quality control strip, the color-measuring fields being printed together with the printed image on a printed sheet. The most comprehensive color measurement process is the spectral process, for example, in accordance with German Industrial Standard (DIN) 5033, Part 4 wherein, within a prescribed wavelength band of 380 nm to 780 nm, 20 to 80 measured values, depending upon accuracy requirements, are obtained for each measuring field. Both the required color coordinates for the selected color space and the necessary colorimetric purities may be arithmetically determined from the thus measured spectral curve by evaluation with color-matching curves and by evaluation with selected color-filter curves. The spectral process entails considerable expense, however. On the one hand, the required division into the individual wavelength bands is costly. On the other hand, it is necessary to carry out extensive processing of the data derived from the measurement. Relatively inexpensive measuring processes and devices have become known heretofore for the determination of colorimetric purities. Moreover, relatively simple devices have become known heretofore for the so-called tristimulus process, in which values for each of three color coordinates are measured according to color-matching curves, for example according to German Industrial Standard (DIN) 5033, Part 6.